Fast forward/rewinding Tv and dvds

Hi I’m a parent to a 6 year old boy with autism. 

He has started wanting to watch the tv or dvds he has on rewind of fast forward. He loves it, he’s bouncing! Arms are going and the joy is clear but when it stops or you turn it off, hell breaks out! 

Does anyone elses chidlren do this? Is it causing him any harm to watch it like this?